Novikov gearing

ABSTRACT

A Novikov gearing comprising at least two gear elements the teeth of each element consisting of an addendum whose profile in the normal section is described by a convex curve, a dedendum and a fillet between the two. A portion of the fillet adjoining the addendum in the normal section has a convex profile with a radius of curvature smaller than a radius of curvature of the addendum.

TECHNICAL FIELD

The present invention relates to mechanical engineering and, moreparticularly, to Novikov gearing.

At present, the use of gearing faces a problem of stepping up the loadcapacity of the gear drive and reducing its specific materialsconsumption. This problem is solved by diverse design and technologicalmethods one of which consists in improving the tooth geometry.

BACKGROUND OF THE INVENTION

Known in the prior art is a Novikov gearing comprising at least two gearelements the teeth of each element consisting of an addendum whoseprofile in the normal section is described by a convex curve, a dedendumand a fillet between them. ("Spur-gear Novikov Gearing with two Lines ofAction" GOST 15023-76, 1976). The fillet has an involute surface whichprovides for a comparatively small clearance between the surfaces ofmeshing teeth in the zone of rolling surfaces of the gear elements.

The gearing of the present invention can be used to improve the contactstrength of only the teeth with a comparatively low hardness of themeshing surfaces.

The use of this gearing with very hard teeth is rather inexpedient sincea small clearance brings the fillet into action comparatively soon and,featuring a low contact strength, it is subjected to progressivecrumbling in the zone of rolling surfaces of gear elements. In addition,an insufficient thickness of the dedendum limits its fracture strength.

Also known in the prior art is a Novikov gearing comprising at least twogear elements the teeth of each element consisting of an addendum whoseprofile in the normal section is described by a convex curve, a dedendumand a fillet connecting the two (SU, A 735855). The fillet has a concaveprofile in the normal section which ensures, in the case of gearelements with very hard teeth, the required clearance in the zone of therolling surfaces of gear elements. The teeth on some parts of thededendum and addendum profile are offset from the axis of symmetry insuch a manner that the thickness of the dedendum is substantiallygreater than the thickness of the addendum which raises the fracturestrength of the dedendum and of the tooth as a whole.

However, further increase of the tooth load capacity is limited by theinsuffucient fracture strength of its addendum.

The main object of the present invention resides in providing a Novikovgearing with its teeth so designed that, while retaining the necessaryclearance between the interacting surfaces of teeth in the fillet zone,said gearing should ensure a relatively higher fracture strength of theaddendum and its load capacity as a whole.

SUMMARY OF THE INVENTION

The object of the invention is accomplished by providing a Novikovgearing comprising at least two gear elements, the teeth of each elementcontaining an addendum whose profile in the normal section is describedby a convex curve, a dedendum and their interconnecting fillet wherein,according to the invention, a part of the fillet adjoining the addendumhas a convex profile in the normal section with the radius of curvaturesmaller than that of the addendum.

The part of the fillet realized according to the invention permitsincreasing the thickness of the critical section of the addendum andthereby increasing its fracture strength while retaining the requiredclearance between the interacting surfaces of teeth in the zone ofrolling surfaces of the gear elements.

BRIEF DESCRIPTION OF THE DRAWINGS

Given below is a description of the present invention by way of examplewith references to the appended drawings in which:

FIG. 1 illustrates a face section through the engaged gear elements;

FIG. 2 is a tooth of the gear element;

FIG. 3 is the tooth profile in normal section;

FIGS. 4 through 6 are fragments of the Novikov gearing according to theinvention in various phases of meshing.

BEST MODE FOR CARRYING OUT THE INVENTION

The Novikov gearing comprises at least two gear elements 1 and 2 (FIG.1). Teeth 3',3" of each of these elements 1 and 2 comprise and addendum4 (FIG. 2), a dedendum 5 and a fillet 6.

The addendum 4 in a normal section of the tooth has a profile describedby a convex curve ab (FIG. 3) which, in a general case, has a variableradius of curvature ρ₁.

The profile of the dedendum 5 (FIG. 2) is described by a concave curvecd (FIG. 3).

The fillet 6 (FIG. 2) has a profile bc (FIG. 3). A part of the fillet 6(FIG. 2) adjoining the addendum 4 has a profile described by a convexcurve be (FIG. 3). The convex curve be has in a general case a variableradius of curvature ρ₂ which is always smaller than the radius ρ₁.Inasmuch as ρ₁ <ρ₂, the thickness of the addendum 4 (FIG. 2) grows by avalue of 2 Δ (FIG. 3) in comparison with the prior art, which is shownby a dotted line in the drawing. This increases a fracture strength ofthe addendum 4 (FIG. 2) and of the tooth as a whole, while retaining ina zone of rolling surfaces 7, 8 (FIG. 1) of the gear elements 1, 2, therequired clearance between the surfaces of the fillets 6 of the meshingteeth in all the engagement phases shown in FIGS. 4 through 6 whichpermits the claimed Novikov gearing to use high-hardness teeth.

A torque is transmitted from the gear element 1 (FIG. 1) to the gearelement 2 as follows.

The driving gear element 1 rotates counter-clockwise. In any one of theconsidered face sections the dedendum 5 (FIG. 4) of the tooth of thedriving gear element 1 (FIG. 1) first interacts with the dedendum 4(FIG. 4) of the tooth of the driven gear element 2 (FIG. 1).

Then the mating teeth (FIG. 5) pass through an intermediate positionwherein the clearance between the fillets 6 in the zone of the rollingsurfaces 7, 8 is at a minimum.

Later on, the addendum 4 (FIG. 6) of the tooth 3' interact with thededendum 5 of the tooth 3" of the mating gear element 2 (FIG. 1). Inthis manner the driven gear element 2 is set in rotation in a clockwisedirection. Owing to the fact, that the addendums 4 (FIGS. 4-6) have athickness increased by the value of 2 Δ (FIG. 3), the stresses arisingin them are smaller than in the addendums used in the prior art, thuspermitting the transmission of a higher torque.

The Novikov gearing realized according to the invention, while retainingthe overall size and weight of the gearing, permits raising thetransmitted load or, at a given load, reducing the material consumptionof the gearing in comparison with the prior art.

INDUSTRIAL APPLICABILITY

The hereinproposed gearing will be utilized with the highest efficiencyin the reduction gears of general mechanical engineering as well as intransport and heavy mechanical engineering.

We claim:
 1. A Novikov gearing comprising at least two gear elementswith the teeth of each element consisting of an addendum whose profilein a normal section is described by a convex curve, a dedendum and afillet interconnecting the two, characterized in that a part (be) of thefillet (6) adjoining the addendum (4) has a convex profile in the normalsection, a radius of curvature (ρ₂) of this section being smaller thanthe radius of a curvature (ρ₁) of the addendum (4).